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Paleo-ecosystems: Early environmental crisis

The Early Toarcian environmental crisis and oceanic

(Early ; 183 Ma BP) Paleo-ecosystems: Early Toarcian environmental crisis

Oceanic anoxic events (OAE):

OAEs represent periods in Earth’s history that were highlighted by widespread organic matter burial, associated with anoxia and/or at a global scale.

The Early Toarcian OAE represent the first of series of OAEs documented throughout the Jurassic and (Jenkyns, 2010).

OAEs were often accompanied by (global) perturbations and events. Paleo-ecosystems: Early Toarcian environmental crisis

In the sedimentary record the Early Toarcian event is expressed by the widespread accumulation of organic matter-rich sediments. Those have been intensively studied throughout Europe (Germany: Posidonia ; France: Schistes Carton; UK: Jet Rock). Early Toarcian bituminous sediments have a thickness of 10 to 40 m and have been deposited within 1 to 1.5 Myr. At some locations black shale deposition lasted longer than 2 Myr. Due to high concentrations of organic matter and the wide spatial and stratigraphic extent, Early Toarcian black can be important sources rocks (e.g. North , Central Paris Basin). Paleo-ecosystems: Early Toarcian environmental crisis

Toarcian bituminous sediments are famous for their excellent fossil preservation. Remains of mainly nektonic organisms can be extremely enriched in distinct horizons, suggesting slow sediment accumulation rates in combination with a low-energetic depositional environment. Paleo-ecosystems: Early Toarcian environmental crisis

extinction level glacial deposits? glacial

K-F global warming sea level OAE LIP (icehouse-greenhouse transition?) perturbation rise Paleo-ecosystems: Early Toarcian environmental crisis

Global paleogeographic reconstruction of the Earth during the Early Toarcian (approx. 183 Ma BP) (Blakey, “Global Paleogeography and Techtonics in Deep Time © 2016 Colorado Plateau Geosystems Inc.”). Shelf areas were bituminous sediments have been accumulated were marked in yellow. The Toarcian CIE has been documented from locations around the globe attesting to a global perturbation of the carbon cycle. Paleo-ecosystems: Early Toarcian environmental crisis

Jurassic climate conditions Paleo-ecosystems: Early Toarcian environmental crisis

The Jurassic as well as the Cretaceous have been commonly associated with overall warm climate conditions during a long-lasting greenhouse mode (Frakes et al., 1992). A low equator-pole temperature gradient has been associated with ice-free polar regions. Paleo-ecosystems: Early Toarcian environmental crisis

The assumption of an overall ice-free Jurassic world was mainly based on floral and faunal distribution patterns. The occurrence of vegetation adopted to warm temperate at high latitudes has been used as evidence for warm (subtropical) climates at polar regions.

Analysis of floral provinces provides only a superficial view on climate conditions, summarizing warm and cold climate conditions over a period of several tenth of millions of years.

e.g. Early Jurassic: 201 – 174 Ma BP (GTS 2012) Paleo-ecosystems: Early Toarcian environmental crisis

Jurassic climate ups and downs – cold (ice-house) – green (hot-house) cycles? Paleo-ecosystems: Early Toarcian environmental crisis

A

B

Glacial-derived deposits of Early Jurassic (Pliensbachian) age have been reported from Siberia as well as from Europe (e.g. Suan etal., 2011; Teichert & Luppold, 2013).

A) glendonites: calcite pseudomorphs (CaCO3 x 6H2O), formation requires tempertures below 4°C, but might also be associated with seeps B) boulder rocks: large blocks in a fine-grained sedimetn matrix, typically associated with ice-related transport. Paleo-ecosystems: Early Toarcian environmental crisis

Climate evolution across the Pliensbachian-Toarcian boundary and throughout the Early Toarcian, inferred from belemnite oxygen data, stomata-indices, floral- characteristics, GDGT-based air temperature reconstructions and sedimentological features (glacial-derived deposits, glendonites). Data are from numerous sources. Paleo-ecosystems: Early Toarcian environmental crisis

Timing of the Karoo-Ferrar volcanism Paleo-ecosystems: Early Toarcian environmental crisis

Toarcian warming

Pl-Toa warming

Correlation of peak activity phases of Karoo-Ferrar volcanism with the Early Toarcian . Data are from numerous sources. Paleo-ecosystems: Early Toarcian environmental crisis

Early Toarcian (s) Paleo-ecosystems: Early Toarcian environmental crisis

The Early Toarcian extinction event in a wider context. The Early Toarcian environmental crisis was associated with profound environmental changes as well as with drastic climate

perturbations (pCO2 x 3; 4-6°C rise in SST). However, high extinction rates were mainly documented for benthic taxa, while nektonic organisms experienced high turnover rates. Paleo-ecosystems: Early Toarcian environmental crisis

The Early Toarcian environmental crisis is associated with multiple extinction events that affected invertebrates and primary producers. Paleo-ecosystems: Early Toarcian environmental crisis

Changes in the species diversity of ammonites from sections from Europe and N-America. A diversity loss has been documented in the kanense zone (time-equal to the D. tenuicostatum and H. serpentinum zones). Also shown extinction and origination rates for ammonites and . Data from Caruthers et al. (2013) and references therein. Paleo-ecosystems: Early Toarcian environmental crisis

High extinction rates were documented for benthic communities that suffered from declining oxygen levels in bottom waters across the shelf . Benthic island (e.g. paleo-swells above the chemocline) allowed benthic organisms to survive. During phases of enhanced bottom water oxygenation benthic taxa resettled previous death zones. Paleo-ecosystems: Early Toarcian environmental crisis

The Early Toarcian Carbon Isotope Excursion Paleo-ecosystems: Early Toarcian environmental crisis

The Pliensbachian to Early Toarcian carbon isotope recoded a negative carbon isotope excursion (Toa-CIE) that has been recoded in coeval sediments around the globe. Local depositional-related processes, however, impacted on the expression of the Toa-CIE. The Toa-CIE was preceded by a CIE at the Pl-Toa-boundary. Paleo-ecosystems: Early Toarcian environmental crisis

The Toa-CIE has been documented in marine and terrestrial organic matter as well as in marine carbonates attesting to a perturbation of the entire exchangeable carbon reservoir (data from Hesselbo et al., 2000). Paleo-ecosystems: Early Toarcian environmental crisis

A negative shift has also been documented in biomolecules originated in marine taxa and in land plant-derived long-chain n- (Schouten et al., 2000; Xu et al., 2017). Data support a global carbon cycle perturbation affecting the marine as well as the atmospheric carbon reservoirs. Paleo-ecosystems: Early Toarcian environmental crisis

Impact of local depositional conditions on the expression of the Toa-CIE in the sedimentary record.

Changes in sedimentation were related to the local depositional setting and to (global?) sea level changes.

Transgressive phases resulted in stratigraphic condensation, while regressive phase in erosive events.

(see Pittet et al., 2014; Ruebsam et al., 2014; 2015) Paleo-ecosystems: Early Toarcian environmental crisis

MTM power spectra for stacked organic carbon isotope record (Luxembourg + Yorkshire) and for the inorganic carbon isotope record from Peniche. Similar spectral peaks have been documented for both records attesting to a similar periodicity. Based on their frequency ratios spectral peaks can be linked to Milankovitch frequencies (LF bpf: low frequency band-pass filter). The presence of an orbitally-forced periodicity in both carbon isotope records indicated that changes in global carbon cycle were potentially associated with climate-sensitive carbon reservoirs. Paleo-ecosystems: Early Toarcian environmental crisis

Statistical analysis (spectral analysis) confirmed the presence of a periodicity in carbon isotope data that can be associated with astronomical cycles (Milankovitch). Paleo-ecosystems: Early Toarcian environmental crisis

Magnitude of the Toa-CIE: The Toa-CIE is associated with a decline in carbon isotope values that range from -3 to -7‰ . Changes in organo-facies (source/preservation of the sedimentary organic matter) can impact on carbon isotope values. Thus, a good correlation is seen for HI and carbon isotope values (Suan et al., 2015). Paleo-ecosystems: Early Toarcian environmental crisis

Corrected for organic matter changes the Toa-CIE can be associated with a decline of about -3 to -4‰ (Suan et al., 2015). Paleo-ecosystems: Early Toarcian environmental crisis

Mechanism proposed to explain the Toarcian CIE:

- Recycling of 12C-enriched carbon in a stratified water column (Küspert, 1976) Toa-CIE not only evident in anoxic/euxinic sediments

- Volcanic outgassing associated with the emplacement of the K-F-LIP (e.g. Brazier et al., 2016)

isotopic composition of volcanic CO2 similar to atmospheric CO2, thus huge amounts of carbon would be required to explain a -3‰ negative CIE

- Intrusion of magmatic dykes into Gondwana coals (Svensen et al., 2007) Orbitally-forced periodicity cannot be explained by carbon emission related to volcanism

- Increased rates of wetland methanogeneis (Them II et al., 2017) fail to explain the recovery of the Toa-CIE as well as the shift from eccentricity to obliquity dominated forcing

- Methane and CO2-release from cryosphere reservoirs (Ruebsam et al., in review) requires the formation of a (expanded) cryosphere during the Late Pliensbachian Paleo-ecosystems: Early Toarcian environmental crisis

Effect of releasing different amounts of carbon with distinct source-specific isotopic composition. A negative CIE can only be produced by emission of 13C-depleted carbon, e.g. from aerobe organic matter (OM) degradation, thermogenic methane, or biogenic methane release. A mixture of these sources is possible as well. On the contrary, unrealistic huge

amounts of volcanogenic CO2 would be required to affect the isotopic composition of the exchangeable carbon reservoir. Paleo-ecosystems: Early Toarcian environmental crisis

Early Toarcian black shales (The Toarcian Oceanic Anoxic Event) Paleo-ecosystems: Early Toarcian environmental crisis

Timing of black shale deposition throughout the Western Tethyan Shelf. The onset of black shale deposition occurred at a similar but at the same stratigraphic interval. Differences in onset and stratigraphic extent of bituminous sediments can be associated with local depositional conditions. Paleo-ecosystems: Early Toarcian environmental crisis

Comparison of Lower Toarcian sections from the Aquitaine Basin and SW German Basin illustrates facies variations. In basin-margin areas and areas of shoals and swells the Pliensbachian–Toarcian boundary is marked by an unconformity (lower sequence boundary). By contrast, sections from the basin centers are characterized by regressive black shales representing the correlative conformity (Röhl & Schmidt-Röhl, 2005). Paleo-ecosystems: Early Toarcian environmental crisis

Black shale deposition throughout the Western Tethyan shelf was linked to the sea level evolution. Here shown a sea level reconstruction that was based on C27/C29 sterane ratios (Frimmel, 2002). Paleo-ecosystems: Early Toarcian environmental crisis

A similar sea level evolution has been inferred from grain-size analysis of terrigenous-derived sediment constituents that was carried out for a core from the central Paris Basin (Hermoso et al., 2013). Paleo-ecosystems: Early Toarcian environmental crisis

Changes in the depositional conditions were controlled by 1) the long-term sea level evolution and 2) environmental instabilities potentially controlled by astronomical cycles (Ruebsam, unpublished). Paleo-ecosystems: Early Toarcian environmental crisis

Geochemical profiles of TOC and Mo abundances and of carbon and molybdenum for Early Toarcian sediments from the Cleveland Basin (UK) (Dickson et al., 2017). Paleo-ecosystems: Early Toarcian environmental crisis

Geochemical profiles of TOC and Mo abundances and of carbon and molybdenum isotopes for Early Toarcian sediments from the Dotternhausen Quarry (S-Germany). In the Cleveland and the S-German Basin TOC-rich intervals showed low Mo-abundances, attesting to depletion of the aqueous Mo- reservoir. Differences in the isotopic composition of the Mo are explained by the degree of Mo- drawdown that was controlled by the redox state (H2S concentration) (Dickson et al., 2017). Paleo-ecosystems: Early Toarcian environmental crisis

Geochemical profiles of TOC and Mo abundances and of carbon and molybdenum isotopes for Early Toarcian sediments from the Belluno Basin (Italy) (Dickson et al., 2017). In contrast to the Cleveland Basin and the S-German Basin that were, both, part of the European Epicontinental Basin System, the Belluno Basin was small depression, situated in the Alpine-Mediterranean sector. Lower TOC and Mo abundances in combination with lower Mo-isotope values were characteristic for preferentially suboxic/anoxic conditions. Paleo-ecosystems: Early Toarcian environmental crisis

Evolution of Mo-abundances and Mo-isotope data during the Toarcian Oceanic Anoxic Event in different sub-basins across the European Epicontinental Basin System. Similar long-term trend reflect secular changes in the isotope composition of the sea water, controlled by the relative size of oxic versus euxinic Mo-sinks. Differences can be linked to local redox and hydrological conditions. Paleo-ecosystems: Early Toarcian environmental crisis shale lack b

Stratigraphic evolution of Mo/TOC ratios and cross-plot of TOC with Mo for Early Toarcian sediments from the Cleveland Basin indicated changes in hydrology and sea water chemistry. Lowest Mo/TOC- ratios can be associated with a severe Mo-depletion to the widespread euxinia and a strong hydrogeographic restriction of the Western Tethyan shelf. The degree of restriction was controlled by the sea level evolution. Moreover, deepwater renewal times, controlled by the persistence of water column stratification, might also impacted on Mo/Toc-ratios (McArthur et al., 2008). Paleo-ecosystems: Early Toarcian environmental crisis

The presence of aromatic (isorenieratane, , ), originated in green bacteria, attested to the presence of H2S-rich waters that have expanded into the photic zone (Jet Rock, Cleveland Basin UK). Also shown indicators of water column stratification and the redox state. Data from French et al. (2014). Paleo-ecosystems: Early Toarcian environmental crisis Paleogeographic map of the Western Tethyan Shelf with focus on the epicontinental basin system and the Alpine- Mediterranean Sector showing the spatial distribution of bituminous sediments and the occurrence of aromatic carotenoids, diagnostic for photic zone euxinia (PZE) (data from Schouten et al., 2000; van Breugel et al., 2006; French et al., 2014).

PZE was a common feature of European epicontinental sub- basins, but has been also reported for a setting in the Alpine-Mediterranean sector of the Eastern Tethyan Shelf (Ruebsam et al., submitted). Paleo-ecosystems: Early Toarcian environmental crisis

Freshwater-driven salinity stratification as driver of shelf sea anoxia and organic matter accumulation. Lower oxygen isotope values at high latitudes reflect lowered sea surface salinities.

0.9 Red numbers indicate MTTC- 0.8 0.6 indices (methylated chromanes) that confirmed lower salinities in the epicontinental basins of the Western 0.5 Tethyan shelf (higher values). 0.6 Brackish conditions at the NW shelf sea either resulted from riverine freshwater discharge of from the inflow of Arctic freshwater. Lower MTTC-indices were documented in areas influenced by saline Tethyan currents. Paleo-ecosystems: Early Toarcian environmental crisis

Freshening of the Arctic due to melting ice caps? Paleo-ecosystems: Early Toarcian environmental crisis

Organo-facies of Early Toarcian black shales (West Tethys Shelf) Paleo-ecosystems: Early Toarcian environmental crisis

Organo-facies evolution of the Posidonia Shale from southern Germany. High TOC- and HI- values confirmed the presence of well-preserved algae/bacteria-derived organic matter. Based on Rock Eval data organic matter can be attributed to kerogen types II and I/II. (Frimmel, 2002, PhD Thesis; Röhl & Schmidt-Röhl, 2005). Paleo-ecosystems: Early Toarcian environmental crisis

Organo-facies evolution of the Posidonia Shale from northern Switzerland. Trends observed match those from the Posidonia Shale of southern Germany (Montero-Serrano et al., 2015). Paleo-ecosystems: Early Toarcian environmental crisis

Organic matter of preferentially marine origin has also been documented for the Schistes Carton (Posidonia Shale equivalent) from the Paris Basin. The distribution of n-alkanes, expressed by the TAR (terrestrial-aquatic ratio) supported a marine organic matter dominance. (Ruebsam, PhD thesis). Paleo-ecosystems: Early Toarcian environmental crisis

n- distribution in different facies intervals of the Schistes Carton from the Paris Basin. Laminated, TOC-rich sediments showed a clear dominance of short-chain n-alkanes that were derived from aquatic organisms (algae, bacteria). Paleo-ecosystems: Early Toarcian environmental crisis

Microphotographs of polished block sections confirmed that in the laminated sediments of the Schistes Carton Fm organic matter is represented by alginites that were enriched in distinct horizons. The presence of Tasmanales remains might be characteristic for the presence freshwater-tolerant algae taxa. Paleo-ecosystems: Early Toarcian environmental crisis

Sediments of the Schistes Carton Fm as well as of the Posidonia shale showed high streroid/hopanoid-ratios, indicating a dominance of eukaryotic primary producers. Paleo-ecosystems: Early Toarcian environmental crisis

Distribution of C27 to C29 steroids representing changes in Early Toarican sediments from S- Germany (Posidonia Shale, left figure) and from the Paris Basin (Schistes Carton Fm, right figure). High concentration of C29-steranes, mainly seen in sediments corresponding to the spinatum and tenuicostatum zones, represent land plant input. Increased abundances of long- chain n-alkanes (nC27-31) supported terrigenous-derived organic matter contributions.

In the Posidonia Shale and the Schistes Caron Fm high abundances of C27 and C28 steroids can be associated with variable contributions of marine and freshwater-tolerant algae, respectively. Sediments associated with more brackish conditions showed high abundances of C28 steroids, derived from Prasinophyte algae. Paleo-ecosystems: upper Kupferschiefer

Literature (some recommendations)

OAEs in general: Jenkyns, H.C., of oceanic anoxic events G3 11, no. 3, Q03004, doi:10.1029/2009GC002788

The Toarcian Oceanic Anoxic Event (black shale deposition): Dickson, A.J., Gill, B.C:, Ruhl, M., Jenkyns, H.C., Porcelli, D., Idiz, E., Lyons, T.W., van den Boorn, S.H.J.M., 2017. Molybdenum-isotope chemostratigraphy and paleoceanography of the Toarcian Oceanic Anoxic Event (Early Jurassic). Paleoceanography 32, 813–829. Hermoso, M., Minoletti, F., Pellenard, P., 2013. Black shale deposition during Toarcian super-greenhouse driven by sea level. Climate Past Discussions 9, 4365 – 4384. McArthur, J. M., Algeo, T.J., van de Schootbrugge, B., Li, Q., Howarth, R.J., 2008. Basinal restriction, black shales, Re- Os dating, and the Early Toarcian (Jurassic) oceanic anoxic event. Paleoceanography 23, PA4217. Röhl, H.J., Schmidt-Röhl, A., 2005. Lower Toarcian (Upper Liassic) black shales of the Central European Epicontinental Basin: a sequence stratigraphic case study from the SW German Posidonia Shale. SEPM Special Publications 82, 165 – 189. Röhl, H.J., Schmidt-Röhl, A., Oschmann, W., Frimmel, A., Schwark, L., 2001. The Posidonia Shale (Lower Toarcian) of SW-Germany: an oxygen-depleted ecosystem controlled by sea level and palaeoclimate. Palaeogeography, Palaeoclimatology, Palaeoecology 165, 27 – 52.

The Toarcian extinction event: Caruthers, A., Smith, P.L., Gröcke, D.R., 2014. The Pliensbachian–Toarcian (Early Jurassic) extinction: a North American perspectiveG. Keller, A.C. Kerr (Eds.), Volcanism, Impacts and Mass Extinction: Causes and Effects, Spec. Pap., Geol. Soc. Am., vol. 505, pp. 225-243. Caswell, B.A., Coe, A.L., 2014. The impact of anoxia on pelagic macrofauna during the Toarcian Oceanic Anoxic Event (Early Jurassic). Proceedings of the Association 125, 383 – 391. Caswell, B.A., Coe, A.L., Cohen, A.S., 2009. New range data for marine invertebrate species across the Early Toacian (Early Jurassic) mass extinction. Journal of Geological Society 166, 859 – 872. Clémence, M.E., Gardin, S., Bartolini, A., 2015. New insights in the pattern and timing of the Early Jurassic calcareous nannofossil crisis. Palaeogeography, Palaeoclimatology, Palaeoecology 427, 100 – 108. Dera, G., Neige, P., Dommergues, J.L., Fara, D., Laffont, R., Pellenard, P., 2010. High-resolution dynamics of Early Jurassic marine : the case of Pliensbachian-Toarcian ammonites. Journal of the Geological Society 167, 21-33. Harries, P.J., Little, C.T.S., 1999. The early Toarcian (Early Jurassic) and - (Late Cretaceous) mass extinctions: similarities and contrasts. Palaeogeography, Palaeoclimatology, Palaeoecology 154, 39 – 66. Paleo-ecosystems: upper Permian Kupferschiefer

The Toarcian Carbon Cycle perturbation: Brazier, J.M., Suan, G., Tacail, T., Simon, L., Martin, J.E., Mattioli, E., Balter, V., 2015. Calcium isotope evidence for dramatic increase of continental weathering during the Toarcian oceanic anoxic event (Early Jurassic). Earth and Planetary Science Letters 411, 164 – 176. Hesselbo, S.P., Gröcke, D.R., Jenkyns, H.C., Bjerrum, C.J., Farrimod, P., Morgenas Bell, H.S., Green, O.R., 2000a. Massive dissociation of gas hydrate during the Jurassic oceanic anoxic event. Nature 406, 392 – 395. Kemp, D.B., Coe, A.L., Cohen, A.,S., Schwark, L., 2005. Astronomical pacing of methane release in the Early Jurassic period. Nature 437, 396 – 399. McElwain, J.C., Wade-Murphy,J., Hesselbo, S.P., 2005. Changes in during an oceanic anoxic event linked to intrusion into Gondwana coals. Nature 435, 479 – 482. Svensen, H., Planke, S., Chevallier, L., Malthe-Sørenssen, A., Corfu, F., Jamtveit, B., 2007. Hydrothermal venting of greenhouse gasses triggering Early Jurassic global warming. Earth and Planetary Science Letters 256, 554 – 566. Them II T.R., Gill, B.C., Caruthers, A.H., Gröcke, D.R., Tulsky, E.T:, Martindale, R.C., Poulton, T.P., Smith, P.L., 2017. High-resolution carbon isotope records of the Toarcian Oceanic Anoxic Event (Early Jurassic) from North America and implications for the global drivers of the Toarcian carbon cycle. Earth and Planetary Science Letters 459, 118 – 126.

Karoo-Ferrar Volcanism: Burgess, S.D., Bowring, S.A., Fleming, T.H., Elliot, D.H., 2015. High-precision geochronology links the Ferrar with early-Jurassic ocean anoxia and biotic crisis. Earth and Planetary Science Letters 415, 90 – 99. Palfy, J., Smith, P.L., 2000. Synchrony between Early Jurassic extinction, oceanic anoxic event, and the Karoo-Ferrar volcanism. Geology 28, 747 – 750.

Toarcian (Jurassic) climate: Dera, G., Brigaud, B., Monna, F., Laffont, R., Pucéat, E., Deconinck, J.-F., Pellenard, P., Joachimski, M.M., Durlet, C., 2011. Climatic ups and downs in a disturbed Jurassic world. Geology 39, 215 – 218. Silva, R.L., Duarte, L.V., 2015. Organic matter production and preservation in the Lusitanian Basin (Portugal) and Pliensbachian climate hot snaps. Global and Planetary Change 131, 24 – 34.

!!!Papers providing a nice overview and a good introduction (for a first reading) were highlighted red.